Modelo morfométrico de los desprendimientos rocosos en el barranco de Fataga, Gran Canaria

Resumo

The The landforms and deposits in slopes are varied (landslides, avalanches, flows, block fields, screes, colluvia). Which fac- tors condition the appearance of one or another depositional typology? This work offers a first approach. For this objective, the Fataga ravine has been chosen. A basin covered by abundant slope deposits . The data used are the geological map; the DEM ; the orthophoto and data gathered during field surveys. The analysis allowed mapping 1971 blocks of planimetric dimensions >2m. The analysis of the morphostructural lines shows a clear dissymmetry between the escarpments of the two margins. The right margin is rectilinear (N-S) and has steep slopes. The left margin has several orientations (N-S; NE-SW) and minor slopes. The heat map analysis shows the existence of 4 zones with the greatest accumulation of blocks: Fataga (150 blocks), Lomo del Pajarillo (92 blocks), Arteara (470 blocks) and Ladera de Los Pinos (16 blocks). Only in 2 of these 4 zones, the blocks cover previous landslides masses. However, the 2 most extensive areas with the highest acumulation are found on the right escarpment of the ravine, where ignimbrite and phonolithic lava flows alternate, both materials with contrasting resistance to erosión. While on the left margin, the intercalations of ignimbrites are scarce. In a first approxima- tion, it seems that the rock falls occur in a later stage than the large landslides, that the runout distance is smaller (they are concentrated in the head scarp) and that the lithological factor is determinant in their spatial distribution, at least in Fataga.